WASHINGTON -- Amid calls for stiffer action against North Korea, the Obama administration told Congress on Tuesday the U.S. response to the Sony Pictures cyberattack was only the first step to further isolate the country over its nuclear and missile programs and human rights abuses.

Earlier this month, President Barack Obama signed an executive order to target officials and front companies of the North Korean government. Rep. Ed Royce, the chairman of the House Foreign Relations Committee, said more needs to be done because most of those blacklisted had already been targeted by U.S. sanctions.

"Last year's cyberattack is estimated to have cost Sony hundreds of millions of dollars in damage," Royce, a Republican, said during a committee briefing on North Korea. "It was a state-sanctioned attack that has many Americans asking, 'If that is what North Korea can do to a movie company, how vulnerable is our critical infrastructure, such as our energy grid? What about my cybersecurity?"'

North Korea insists it had nothing to do with the cyberattack on Sony Pictures Entertainment over the movie, "The Interview," which depicts an assassination attempt on the North Korean leader. North Korea's deputy U.N. ambassador, An Myong Hun, on Tuesday called for a joint investigation with the United States.

"It is totally arbitrary and out of established hostile policy against my country to impose any kinds of pressure against my country, which we cannot accept at all," the ambassador said at a news conference at the United Nations.

Royce said the U.S. needs to step up and target financial institutions in Asia and elsewhere that are supporting the North Korean government.

Royce said that last year the House passed legislation to ramp up the financial pressure on North Korea, pressing the country to be designated a primary money laundering concern -- as has been done with Iran -- curtailing its sale of weapons and stepping up inspections of North Korean ships, among other steps. He stressed that North Korea should be denied the hard currency it needs, for example, to expand its missile program.

The Senate did not act on the legislation before adjourning last year, but Royce said the Republican-led House will attempt to push it again.

North Korea and the U.S. remain technically in a state of war because the 1950-53 Korean War ended with an armistice, not a peace treaty. The rivals also are locked in an international standoff over North Korea's nuclear and missile programs and its alleged human rights abuses. A United Nations commission accuses North Korea of a wide array of crimes against humanity, including murder, enslavement, torture, imprisonment and rape.

"Together with the international community, we're using the full range of tools at our disposal to make clear to the DPRK that abandoning its nuclear weapons, provocative actions and human rights abuses is the only way to end the political and economic isolation," Sung Kim, deputy assistant secretary of state and special representative for North Korea policy, told the committee members. DPRK refers to the North's official name, the Democratic People's Republic of Korea.

"We have made clear that we will respond to the DPRK's misbehaviour. The executive order signed by the president on Jan. 2 is an important new tool. It responds to the attack on Sony Pictures, but also provides a framework for addressing the full range of DPRK illicit behaviour."